The major goal of this research project is to further study the natural course of histoplasmic choroiditis in primates by serial fundus photography, fluorescein angiography, fungal cultures, and histopathology of enucleated eye. We will be particularly interested in the histopathology of late natural course lesions, with emphasis on duration of lymphocytic foci and organisms in areas of choroiditis. In addition, serial sections will be prepared to assess damage or changes in Bruch's membrane and the retinal pigment epithelium. Attempts to reactivate clinically inactive atrophic choroidal foci will be carried out utilizing such techniques as repeated histoplasmin skin testing, intravascular challenge with histoplasma antigen, re-infection, non-specific stimulation of immune response using concanavalin A and lipopolysacchride, and mechanical irritation of Bruch's membrane by photocoagulation. The role of inflammation and/or subretinal neovascularization in the development of such activation will be studied by serial fluorescein angiography, fundus photography, serum antibody, titres, lymphocyte stimulation, and histopathology. Ultimately, when models of reactivation have been established, trials of appropriate therapy will be considered.